This invention relates to the preparation of tetraphenolic compounds. In one aspect, the invention relates to a process for the continuous preparation of a tetraphenolic compound in a heterogeneous reaction mixture. In a specific embodiment, the invention relates to the continuous catalytic preparation of the tetraphenol of xylene from terephthalaldehyde and phenol.
Tetraphenolic compounds such as the tetraphenols of ethane and xylene are starting materials for the preparation of multifunctional epoxy resins for coatings and electronics applications. The tetraphenol of ethane, for example, can be prepared by the acid-catalyzed condensation reaction of glyoxal and phenol in a homogeneous liquid reaction mixture. Typical acid catalysts include aqueous hydrochloric acid and oxalic acid. When aqueous HCl is the catalyst for the reaction, it is typical to neutralize the acidic reaction product mixture by addition of a base such as sodium bicarbonate. The neutralized product mixture is then distilled for removal of excess phenol and by-products. The product yield of such a process is typically low, and the product is often contaminated with by-product from the sodium neutralizing agent. Use of strong acids also requires the use of special equipment including a glass-lined reactor, adding to the expense of the process.
It is therefore an object of the invention to provide a process for preparing tetraphenolic compounds. In one aspect, it is an object of the invention to provide a cation exchange resin-catalyzed process for preparing a tetraphenolic compound. In a further aspect, it is an object of the invention to improve product yield and reaction rate in the preparation of the tetraphenol of xylene.